IOS ESSENTIALS Lecture 04 Jonathan R. Engelsma, Ph.D.
iOS Bootcamp: learning to create awesome apps on iOS using Swift (Lecture 04)
Jul 31, 2015
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IOS ESSENTIALSLecture 04
Jonathan R. Engelsma, Ph.D.
TOPICS
• Model / View / Controller
• Understanding ViewControllers and their life cycle.
• Overview of commonly used iOS ViewControllers
MODEL/VIEW/CONTROLLER
Model
Controller
View
Our iOS code is broken up into 3 different components(Inspired by Paul Hegarty’s very excellent MVC lecture.)
MODEL/VIEW/CONTROLLER
Controller
View
The MODEL is the data our app produces/consumes.
Model
MODEL/VIEW/CONTROLLER
Model
Controller
The VIEW is what the user sees and interacts with on screen.
View
MODEL/VIEW/CONTROLLER
Model View
The CONTROLLER manages the model and the view.
Controller
MODEL/VIEW/CONTROLLER
Model
Controller
View
Controller can manipulate the model directly.
MODEL/VIEW/CONTROLLER
Model
Controller
View
Controller can manipulate the view directly.
Takes place via an “outlet”
MODEL/VIEW/CONTROLLER
Model
Controller
View
Model / View should NEVER talk directly to each other!
MODEL/VIEW/CONTROLLER
Model
Controller
View
Views can sort of talk to controller, but only in a very controlled manner!
Controller defines an action.
View is wiredup to call action.
MODEL/VIEW/CONTROLLER
Model
Controller
View
Controller serves as the View’s delegate and data source via Protocols
DelegateData Source
GREETING DEMO
DEMO!!
VIEW CONTROLLERS• View controllers manage a screen’s view hierarchy and the
segues between view controllers.
• The “glue” between views and models in MVC.
• View controllers:
• initialize and setup models
• populate the view hierarchy with views
• coordinate with the view hierarchy (delegate)
• format data for the views (data source)
VIEW CONTROLLER LIFECYCLE
• Recall the methods generated when we created our first app:override func viewDidLoad() { super.viewDidLoad() // Do any additional setup after loading the view, typically from a nib. self.configureView() }
override func didReceiveMemoryWarning() { super.didReceiveMemoryWarning() // Dispose of any resources that can be recreated. }
• These are methods that help us coordinate with the controller’s lifecycle.
VIEW CONTROLLER LIFE CYCLE
• Understanding the view controller life cycle allows us to properly manage the controller’s models and views.
• Whenever a view controller’s view property is accessed a chain of events is triggered.
https://developer.apple.com/library/IOS/featuredarticles/ViewControllerPGforiPhoneOS/ViewLoadingandUnloading/ViewLoadingandUnloading.html
View property Accessed
Viewexists? loadView
Return view
loadViewoverriden?
Run loadView
Storyboard?
Load from storyboard
EmptyView
viewDidLoad
YY Y
N
N N
VIEW CONTROLLER METHODS
Method Name DescriptionviewDidLoad View has finished loading.
viewWillAppear View is about to appear.viewDidAppear View just appeared.
viewWillDisappear View is about to disappear.viewDidDisappear View just disappeared
didRecieveMemoryWarning Low memory conditions detected.
UITabBarController UICollectionViewController UITableViewController
UINavigationController
LIFECYCLE & STOPWATCH DEMOS
DEMO!!
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